Medium-sized businesses with between 50 and 500 employees were the biggest job creators, adding nearly half of all new jobs. Meanwhile, smaller businesses added about 25,000 employees and larger businesses added 88,000 employees.

The report comes a day before the government’s official monthly jobs report, but economists are skeptical about comparing the two reports. ADP looks at only private sector employers, whereas the Labor Department also includes government jobs.

Meanwhile, seasonal adjustments in the month of December often make for a wide disparity between the two reports. Last year for example, ADP predicted private sector employers added 325,000 jobs. A day later, the Labor Department said they only created 212,000.

And in December 2010, ADP’s numbers for private payroll growth were 184,000 higher than the government’s official numbers.

Economists surveyed by Briefing.com predict that Friday’s report will show 150,000 jobs were created in December, including the private sector and the government.

Hiring at that level is in line with the monthly average for 2012 overall, and marks no major change in job market conditions.